//创建二维数组
var arr = [
  ['北京','海淀','东城','西城'],
  ['山东','济南','青岛','烟台'],
  ['河北','石家庄','秦皇岛','保定'],
  ['广东','广州','深圳','东莞']
];
for(var i=0;i<arr.length;i++){
  //console.log(arr[i]);
  //遍历arr[i]--数组
  var str='';
  for(var j=0;j<arr[i].length;j++){
    //console.log(arr[i][j]);
	str+=arr[i][j]+',';
  }
  console.log(str);
}





